Synthesis of sea-urchin-like Bi2S3 hollow microspheres for highly efficient removal of Ag+ with extremely low acidity

Abstract

In this study, we report that the high-quality sea-urchin-like Bi2S3 hollow microspheres (denoted as SUBHM), prepared on a large scale by a simple hard-templated engaged polyol process, were used to remove silver ions under extreme pH conditions. The adsorption of silver ions (Ag(I)) as a function of time, solution pH, temperature and initial Ag(I) concentration was studied by batch experiments. Various characterization tools, such as X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV–Vis absorption spectrophotometry, were applied to confirm the structural and compositional changes of the adsorbents during the removal process. The kinetic studies showed that the adsorption process exhibited a fast adsorption rate (98.9% removal within 3 min and 99.8% removal within 10 min, with a 500 ppm initial concentration), which was described well by pseudo-second-order kinetics. The maximum adsorption capacity of Ag(I) was fitted perfectly by the Langmuir adsorption isotherm method at 298 K and pH 1.22. In addition, SUBHM showed an excellent chemical stability under extreme pH conditions, which led to the effective removal of Ag(I) over a broad pH range (from 0.4 to 6).